When the pusher incorporates a fluid dispenser orifice, it is frequent for the actuator rod to define an internal fluid duct, and for the pusher to define an internal fluid channel that leads to a dispenser orifice, the connection means butt joining the duct to the channel in leaktight manner. In general, the pusher defines a connection sleeve that forms the inlet of the internal fluid channel. Conventionally, the connection sleeve is force-fitted around the free end of the actuator rod 23, thereby forming a leaktight engagement.
In entirely conventional manner, the body and the actuator rod co-operate with each other to define a pump or valve chamber of volume that is variable. The inlet of the chamber is provided with an inlet valve and the outlet of the chamber is provided with an outlet valve. When the chamber is full of fluid, driving the actuator rod axially into the body causes the volume of the chamber to decrease and the fluid that it contains to be put under pressure. The inlet valve is forced into its closed state and the outlet valve opens under the effect of the pressure. The fluid may thus be discharged through the internal duct of the actuator rod and through the internal channel of the pusher for dispensing at the dispenser orifice. This design is entirely conventional for a pump or a valve in the fields of perfumery, cosmetics, and pharmacy.
In order to establish leaktight engagement between the pusher and the actuator rod, it is necessary to apply sufficient force on the pusher towards the actuator rod. This causes the actuator rod to be driven into the pump body, and causes a dose of fluid to be dispensed when the pump chamber is full of fluid. The operation of engaging the pusher on the actuator rod may thus cause fluid to leak between the actuator rod and the pusher, in particular when leaktight engagement has not yet been formed while fluid is being dispensed. In any event, leaktight engagement on the actuator rod requires the actuator rod to be driven in.